html,
body {
    width: 100%;
    margin: 0;
    height: 100vh;
    user-select: none;
}

#app {
    width: 100%;
    height: 100vh;
    font-family: Microsoft YaHei-Bold, Microsoft YaHei;
    font-size: 12px;
}
img{
    position: relative;
}

img::after {
    content: '我是一张替换图片图片';
    position: absolute;
    left: 0;
    top: 0;
    right: 0;
    bottom: 0;
    background-color: #ccc;
    display: flex;
    align-items: center;
    justify-content: center;
}